1. Field of the Invention
This invention relates in general to storage devices and more particularly to a method and apparatus for aggregating storage devices.
2. Description of the Prior Art
Information is rapidly becoming the most valuable asset of most companies. At the same time, managing and protecting information is becoming dramatically more complex and difficult due to the explosion in data storage requirements and the shift from centralized to distributed storage of data on enterprise networks. In addition, users are storing more and more data on their desktop and laptop computers. The exploding storage requirements are continually outgrowing the storage capacity of servers and workstations. As a result, storage capacity must be continually updated, which is costly and disruptive to users.
Magnetic storage is a popular means of storage because stored data persists even without a continual source of electricity, and because this type of data storage is affordable for many applications. Magnetic storage is frequently implemented on a more massive scale. For example, some storage systems aggregate a large number of storage devices into a single storage system within a single enclosure, utilizing control electronics, power supplies, cooling features, and other infrastructure that is common to all drives in the system. Further, such storage devices may encounter performance constraints. For example, such performance constraints may be related to server processing speeds, hard disk drive (HD) access rates, limitations on areal density of the storage media and the storage networking link speed. Historical solutions to these problems included shrinking HD platter sizes to allow greater spindle speeds, although this solution is reaching the level of diminishing returns, and grouping HDs using redundant arrays of inexpensive disks (RAIDs), and other technologies to place segments of sequentially addressed data at similar places on multiple HD platters, and on multiple HDs (using RAID striping).
Currently, hard disk array enclosures in the area of enterprise-class disk array architecture are dominated by 3.5-inch form factor drives, stacked on their sides in a row of 10-15 HDs. Each HD is housed in a carrier (HDC), which protects the drive during normal handling and allows guided insertion of the HD into a storage system, allowing the rear connectors to link up properly to the storage system. Today, HDCs each hold 1 HD and are housed in a storage system having power aggregation, heat dissipation aggregation and storage network connection sharing. In a storage system multiple power supplies (usually 2) are aggregated and made available to each HDC and to the electronics of the storage system. Heat is dissipated from the storage system by arranging HDs in a larger storage system, 3U high (1U=1.75 inches) by 19 inches wide, so that large fans can be placed at the rear of the storage system to allow cooling of the HDs. Storage systems use storage network connection sharing because each HD can only access data at a fraction of the potential bandwidth of the connection to the storage network. Therefore, HDs are placed on a network internal to the storage system. The storage system has a small number of connections, typically two, to the storage network. Although both connections are used for performance, one is essentially a backup in case the other one has a link failure. Typically, HDs are addressable through the storage system connections, although some storage systems enhance the enclosure electronics to provide Redundant Arrays of Inexpensive Disks (RAID). This offers logical disks through the storage system connections that are internally mapped to the physical disks.
Aggregating HDCs does not overcome the previously mentioned performance problems of server processing speeds, areal density of HD storage media and storage networking link speed. In attempting to solve these problems, attention must be paid to cost per gigabyte in implementing solutions. HDs offer “x” gigabytes of storage in a finite amount of space, for a finite amount of power, with a finite complexity of connection, and as a result cost per gigabyte is impacted by the challenges of space utilization, power needs and heat dissipation, and electrical connection.
Space utilization affects cost per gigabyte because designing and implementing the DE incurs cost. Where currently available DEs are used, design and implementation costs may be eliminated thereby eliminating the space utilization factor related to DE design and implementation in calculating cost per gigabyte. Further, when extra space is needed to house additional storage, cost per gigabyte is affected. However, if the same amount of space can be used to store a greater amount of storage, then space utilization cost per gigabyte is reduced.
HDs require an amount of power to operate. With an increasing amount of power used in a space, there is an increased amount of heat generated in that space, both affecting cost. HDs generally need to run continuously because an idle HD has a higher probability of failure proportional to idle time. As a result of the necessity for HDs to be continuously active, heat is continuously generated. But, excessive heat destroys electronic media and reduces the reliability of managing electronics. Thus, the amount of power used by the HD directly incurs cost, and compensating for heat generation, by implementing cooling fans for example, incurs cost by its use of power and increase in design complexity. Each of these factors directly increases cost per gigabyte for the storage system.
Electrical connections like parallel ATA and parallel SCSI HD connections involve 40+ pins per HD. Fibre Channel uses fewer pins but has its own connectivity challenges and cannot be implemented at a low cost. The complexity of the electrical connectivity directly impacts cost per gigabyte by increasing the design/implementation cost of the storage system.
It can be seen that there is a need for a cost effective method and apparatus for aggregating storage devices.